Many electromagnetic devices, including various sensors (e.g., linear variable differential transducers), motors, and actuators (e.g., solenoids) employ one or more coils of insulated wires. Each insulated wire typically includes at least one elongated conductor sheathed within an insulative coating. The elongated conductor is typically formed from an electrically conductive alloy or pure metal, such as nickel, copper, aluminum, or silver. The insulative coating is commonly formed from a dielectric material, such as polyimide, polytetrafluoroethylene, (e.g., Teflon®), and polyvinyl chloride (PVC). During manufacture, the dielectric material may be applied to the elongated conductor via a spraying, drawing, or electrolytic coating processes. After application of the dielectric material, the coated wire may then be cured and formed into a desired shape (e.g., wound into a coil shape).
Although well-suited for use in a variety of applications, many conventional insulated wires are unsuitable for use in high temperature operating environments (e.g., exceeding 240° C.) due to working temperature limitations of the insulative coating. Polyimide insulated wires, for example, are relatively inexpensive and simple to manufacture, but have a maximum continuous working temperature limit of about 240° C. Similarly, Teflon® has a maximum continuous working temperature limit of approximately 260° C. In addition, the utilization of Teflon® and other similar dielectric materials may result in an undesirable increase overall wire thickness and cost.
The temperature stability of insulated wires may be increased by utilizing certain other dielectric materials to form the insulative coating; however, these alternative materials are also limited in various respects. For example, silicon oxides may be utilized to form an insulative coating that is more resistant to high temperature operating conditions; however, silicon oxide insulated wires are relatively inflexible, which renders such wires difficult to utilized in electromagnetic devices wherein the wires need to be bent, coiled, or otherwise formed after application and curing of the insulative coating. This is especially true for coiled-wire devices (e.g., sensors, motors, and actuators) of the type described above. With respect to such coiled-wire devices, the maximum operating temperature of the insulated wire may be increased by utilizing an alternative manufacturing technique wherein the elongated conductor is first wound into a coil, a dielectric coating is applied over the wound wire, and the entire assembly is subsequently cured. Such post-winding cure procedures are, however, undesirably costly and time consuming. Furthermore, to reliably implement such post-winding cure procedures, the entire electronic assembly (e.g., circuit boards, sensors, etc.) must be able to withstand exposure to high cure temperatures, which may exceed the operational limit of other components.
Considering the above, it is desirable to provide an insulated wire suitable for use within high temperature environments that is sufficiently flexible to be formed into a desired shape (e.g., a coil) subsequent to application and curing of the dielectric coating. It is further desirable for such an insulated wire to resist attrition of its insulative coating due to self-abrasion that may otherwise occur in applications wherein the wire is wound into a multi-turn coil. Lastly, it is desirable to provide methods for producing such an insulated wire that are relatively inexpensive and straightforward to implement. Other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.